The economic usage of millimeter (mm) and terahertz (THz) waves has significantly increased in recent years. All over the world, the practical usage of mm and THz waves for communication and radar applications is intensively worked on. This frequency range has many important advantages. The most illustrative example is the future wireless video signal transmission, e.g. to beamers, by using the new high-speed WLAN standard IEEE802.11ad in the 60 GHz band, as well as the application of 79 GHz automotive radar for detecting the surroundings of a car in autonomous driving.
However, some physical characteristics of the mm waves are disadvantageous, such as low range due to high attenuation and reflection at many solid and liquid materials. However, by specific technical developments, these disadvantages can be avoided or can even be used specifically for the desired application (e.g. near-field communication).
The central issues in these technical developments are the antennas for optimum transmission and reception of mm and THz waves. Accordingly, antenna development and the involved measurement technology for characterizing the antenna characteristic will play a significant role in the usage of mm and THz waves.
Nowadays, shielded rooms are commonly used for measurement-technology characterization of antennas for mm wave applications. FIG. 15 shows exemplarily a shielded room, as it is currently used in the Institute of Fraunhofer IZM. The antenna measurements are currently very time-consuming and have to be performed by experienced high-frequency (HF) specialists.
These expensive shielded rooms and the need for highly qualified HF specialists for performing the measurements as well as the high time effort for performing the measurements are obstacles for the development of mm and THz wave antennas and the quality control of these antennas in production.
The conventional technology [1] to [5] knows scientific and commercial systems. The systems in science are all based on a similar principle. A linearly polarized standard gain horn antenna is positioned on a rotatable arm. With the help of the arm, the standard gain horn antenna is guided around the antenna to be measured.
Commercial systems are exclusively offered in shielded rooms and together with shielded rooms, respectively, and these systems are based on frequency-domain measurement methods and near-field measurement methods, respectively.
Thus, known systems need a free field for obtaining reproducible measurement results to obtain reliable statements on the characteristics of an antenna under test. However, high effort is needed to realize such free-field conditions artificially, namely by providing a so-called an anechoic room. Thus, a conventional measuring station needs a lot of space (exemplary dimension of the shielded room at the Fraunhofer IZM is 5×3 m2), in particular compared to the actual size of an antenna under test for the millimeter and terahertz range. Additionally, expert personnel are needed for performing the HF measurements.